The present invention relates to a lamination for a linear motor and to an arrangement that provides a more secure mounting of said laminations.
Linear motors are well known devices, in which one of a coil or magnet element is mounted to a fixed member, and the other element is mounted to a member to be moved. The linear motor has an array of inner laminations and an array of outer laminations, between which the magnet element is moved. Electric current is applied to the coil, which generates magnetic lines of force to interact with the magnet element to produce linear motion of the movable member. Such linear motors are generally used in refrigeration compressors in which the movable member is defined by the piston of the compressor and the magnet element is mounted to said piston. The coil is fixedly mounted to an external portion of the compressor structure that forms the cylinder, inside which the piston is reciprocated upon operation of the linear motor. Linear motors are used in other devices in order to, for example, reciprocate a shaft inside a bushing, with the movement of the shaft performing work in a machine.
FIG. 1 of the appended drawings illustrates an inner lamination 30 of a known construction for a linear motor. This inner lamination 30 is planar and usually stamped from a piece of sheet metal material having magnetic characteristics. The inner lamination 30 has a generally xe2x80x9cUxe2x80x9d shaped base 31 incorporating a pair of coplanar wings 33 having a pointed end that may be defined as a flat tip 34, as illustrated. Each inner lamination 30 has a recess or a cut-out 36, into which is mounted a toroidal coil (not shown), to which electric current is applied. FIGS. 2 and 3 illustrate the mounting of inner laminations 30 in a circular array to form the stator of a linear motor, and the bases 31 of the inner laminations 30 are secured around a first fixed member, which may be defined by a bushing, in which a shaft is reciprocated, or by the cylinder of a compressor, within which a piston is reciprocated. An array of outer laminations 20 is placed around a second fixed member, which may be defined by the inner face of a cup that houses the bushing or the compressor cylinder.
In the embodiment of the inner laminations 30 illustrated in FIGS. 1 and 2, the flat tip 34 of the upper wing 33 defines the available area for welding or gluing the array of laminations to a mounting member such as a cylinder flange or an annular connecting element, as described ahead. This substantially limited surface area, defined by the thickness of the lamination itself, may not be adequate to assure good fixation and mounting of the array of inner laminations 30.
One way to form the array of inner laminations 30 in a linear compressor is shown in FIG. 4. In this construction, a cylinder 10 of the compressor has a center bore in which the piston (not shown) is reciprocated. Around the outer periphery of part of the cylinder 10 are mounted the bases 31 of an array of inner laminations 30, which are secured to the external periphery of the cylinder 10 or any other suitable support means mounted to the cylinder. The laminations of the array of outer laminations 20 are in the form of individual pieces mounted around the interior of a circular wall of a cup (not shown). The upper ends of the outer laminations 20 are also in the form of a flat tip affixed to the lower face of a flange 10a incorporated to and extended radially from the cylinder 10, and said fixation to the lower face of the flange 10a is achieved by an adhesive or by welding. Alternatively, the outer laminations 20 can be mounted to a support provided on the wall of the cup, within which the cylinder is positioned.
FIG. 5 shows another type of lamination mounting arrangement for the motor of a linear compressor, such as described in the co-pending patent application of the same applicant. In the mounting illustrated in FIG. 5, the cylinder 10 of the compressor does not have the flange boa, which makes the manufacture of the cylinder relatively complex and expensive. In this embodiment of FIG. 5, the inner laminations 30 have their wings 33 provided with flat tips 34. The ends of the outer laminations 20 are also flat in this embodiment, in which a connecting ring 40, of a nonmagnetic material, is mounted to the upper ends of the inner laminations 30 and the outer laminations 20, and affixed to said ends by adhesive or by welding. Thus, there is provided a suspension mounting of the outer laminations 20 through the connecting ring 40 that is attached to the inner laminations 30, these in turn being attached to the cylinder 10.
The area, by which either the lower face of the flange 10a of the cylinder 10 of the structure illustrated in FIG. 4 or the lower face of the connecting ring 40 of the construction illustrated in FIG. 5 can be attached to the upper end of the inner laminations 30 and the outer laminations 20, is only that defined by the thickness of each lamination. Where the laminations are thin, the mounting is not very stable. In the case of the outer laminations 20, the end fixation area of each lamination is not critical due to the relatively small radial width of the outer laminations 20, which allows maintaining them very close to each other throughout the radial width thereof. In this case, the end fixation areas are practically associated to each other, facilitating the fixation thereof by glue or welding.
Nevertheless, in the case of the inner laminations 30, the radial width thereof makes them divergent relative to each other, from the inner edge affixed to the cylinder 10 towards the outer edge 35. The outer edges 35 are quite separated from each other, and so are the flat tips 34 of the upper ends, avoiding the fixation of all said flat tips 34 as a single surface. Thus, for the inner laminations 30, the upper fixation area is critical to provide for better fixation of said laminations.
Another problem of the constructions described above is the difficulty of maintaining the inner laminations 30 spaced apart from each other by a certain angle around the entire external periphery of the compressor cylinder.
Accordingly, it would be desirable to provide a lamination having a structure that can be arranged in a circular array, such as that defined by the inner laminations 30 and the outer laminations 20 of a linear motor, in order to provide a larger surface area for fixation of at least one of the ends thereof to another member.
It is an object of the present invention to provide an improved structure for a lamination, which is to be arranged in a array of laminations, such as used in a linear motor, in order to provide a larger surface area for fixation of at least one end of each lamination of the array to an external member.
In accordance with the invention, a lamination for a linear motor is formed of a piece of metal having magnetic properties and presenting a structure comprising a base to be placed adjacent to a fixed member, such as the outer surface of a bushing or the cylinder of a linear compressor, or against the inner surface of another fixed member, such as a cup to house the bushing or the cylinder. The lamination incorporates at least one coplanar wing extending from the base and having an end that is bent at an angle in relation to the common plane of the base and the wing, to form a flap with a surface area corresponding to the size of the flap. A plurality of laminations is arranged in a circular array to form the linear motor. The flaps are provided at the upper end of the laminations of the array, in order to lie in a common plane to form a relatively large surface area for mounting of al external member to said array of laminations.